Re: [PATCH] release_resource() check for NULL resource

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Mon, Oct 03, 2005 at 03:43:50PM +0300, Pekka Enberg wrote:
> Usually yes but it makes releasing partial initialization much simpler
> because you can  reuse the normal release counterpart. For example,
> 
> static int driver_init(void)
> {
>      dev->resource1 = request_region(...);
>      if (!dev->resource1)
>              goto failed;
> 
>      dev->resource2 = request_region(...);
>      if (!dev->resource2)
>              goto failed;
> 
>      return 0;
> 
> failed:
>      driver_release(dev);
>      return -1;
> }
> 
> static void driver_release(struct device * dev)
> {
>      release_resource(dev->resource1);
>      release_resource(dev->resource2);
>      kfree(dev);
> }
> 
> Many drivers have the release function copy-pasted to init with lots
> of goto labels exactly because release_region, iounmap, and friends
> aren't NULL safe.

And the above is buggy.  request_region() allocates memory.
release_resource() unregisters the resource but does _not_
free the allocated memory.

On the other hand, release_region() is the counter-part of
request_region() and should be used to release resources
created by request_region().

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core